The Gauge System in Shotguns: "Gauge" is a archaic English method of measurement of bore diameter based on the quantity of lead round balls of a certain size that would equal one pound in weight. For instance, a 12 gauge shotgun has a bore diameter of .729", and 12 lead round balls of this diameter will weigh one pound. Thus, the smaller the number, the larger the bore diameter. The one exception is the .410 shotgun, which is the true bore size in thousandths rather than a gauge measurement.

Service Charges in Shotguns: The British service charges for breech loading smooth bore guns, as listed in W.W. Greener's book, The Gun and It's Development (9th edition, published 1910) is as follows:

Gauge

Black Powder in Grains

Black Powder in Drams

Shot

10 ga.

116 grains

4-1/4 drams

1-5/8 oz.

12 ga.

89 grains

3-1/4 drams

1-1/4 oz.

14 ga.

82 grains

3 drams

1-1/8 oz.

16 ga.

75 grains

2-3/4 drams

1 oz.

20 ga.

68 grains

2-1/2 drams

7/8 oz.

28 ga.

55 grains

2 drams

3/4 oz.

One Dram equals 27 1/2 grains.

This may be used as a guideline for muzzle loading guns as well, although I recommend starting with a lighter load and working up. For instance, I use a 16 gauge load in a 12 gauge muzzle loader and find that it works very well, plus it is more pleasant to shoot. Outside of turkey or waterfowl hunting, it is not necessary to shoot full service charge. The standard British velocity with black powder was 1050 f.p.s. which was found to give the best patterns.

2. Seat a .125" thick over powder “A" card firmly on the powder charge. This thick card seals the bore, and keeps the powder dry.

3. Insert a thick fiber “C" wad and press it in place. Soak fiber wads in cooking oil when hunting, or use our Bore Clean when trap shooting. Or try our new pre-lubed wads available is selected sizes only.

4. Pour a measured lead shot charge into the shotgun. Never use steel shot in antique muzzle loading guns! Remember increasing the shot charge decreases velocity.

5. Seat an overshot “B" card last. This stiff card holds the shot in place, but won't leave a hole in your pattern.

6. Cap your nipple only when on the firing line or in your hunting field.

Loading through Choke Tubes: This is a problem that never existed in the muzzle loading era. Choke boring was not widely used until 1875, which was well into the breech loading era, where you did have to worry about getting down past the choke with the wads. After choke boring became available in breech-loaders, some live pigeon shooters who wanted to continue using their muzzle loaders had their guns jug (or recess) choked. This consisted of reaming a recess into the bore that was larger than the bore diameter, about 6" long, starting back about an inch from the muzzle. The shot hit this area, expanded, and then forced the shot back down to original bore size, creating the same choking effect as our modern constriction style chokes. Now, some new muzzle loading shotguns have screw in chokes. This provides the choking effect, but loading down through them becomes a problem. The difference is, that the wads used in the jug choke were matched for the bore size and going through the recess was no problem. A full choke 12 gauge gun has a constriction of .040", which makes the bore size at the muzzle a 14 gauge. Since the overpowder (nitro) card seals the powder gases, it has to be 12 gauge or the gas will blow by it and the load will not create sufficient pressure to shoot well. There are two possible solutions to this. First, load your gun before you screw in the choke tubes. This may work if you are hunting and don't expect to fire too many rounds, or, second, place the nitro card on it's edge and force it down through the choke tube with a ball starter, then tip it over flat once you have gotten past the choke and seat it on the powder. This does the least amount of damage to the wad, by only flattening it on 2 sides. The fiber wad can be undersized, for instance, using a 14 gauge fiber in a 12 gauge full choke gun, as the fiber would be destroyed ramming it through the choke. A 12ga. overshot card is thin and flexible enough to go through a choke tube without damage.